Haber, E. and Members of the Subcommittee for Vascular Plants, Mosses, and Lichens. 1995. Guidelines for the preparation of COSEWIC Status Reports on vascular plants, mosses, and lichens. Committee on the Status of Endangered Wildlife in Canada (COSEWIC), Ottawa. 16pp.

Hill, G.a. 1959. A ready reference to the description of the Land of Ontario and its productivity. Department of Lands and Forests.

Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. Second edition. Volume 1-checklist. Biota of North America Program and the North Carolina Botanical Garden. Timer Press, Portland, Oregon. 622 pp.

Urquhart, F.A. and N.F. Urquhart. 1979. Breeding areas and overnight roosting locations in the northern range of the Monarch Butterfly (Danaus plexippus plexippus) with a summary of associated migratory routes. The Canadian Field-Naturalist 93:41-47.

Woodson, R.E., Jr. 1954. The North American species of Asclepias L. Annals of the Missouri Botanical Garden 41:1-211.

Wyatt, R. 1976. Pollination and fruit-set in Asclepias: a reappraisal. American Journal of Botany 63:845-851.

4.2 Collections Consulted

The following herbaria were consulted for records of Milkweeds in Ontario in 1983. All Ontario specimens from these herbaria were examined by C. Keddy for the Ontario Rare Plant Atlas (Argus & Keddy, 1984). The herbaria at CAN and DAO were also checked in 1996 by the present author for records of rare Ontario Milkweeds received after 1983.